1. Field of the Invention
The present invention relates to an electric device which notifies an external device of status information of the electric device and a control method in the electric device.
2. Description of the Related Art
Event notification registration processing is known as processing of notifying a particular external device of occurrence of event in an electric device. Japanese Patent Application Laid-Open No. Hei 11-203094 discloses an electric device which receives an event notification registration request and registers an external device specified in the request as a notification destination, and further, upon occurrence of event in the electric device, notifies the registered external device of the occurrence of the event. Further, in this electric device, the registration of the external device is deleted from a registration table after an elapse of a predetermined time period.
In a system having such electric device and external device, the external device issues an event notification registration request to the electric device so as to obtain status information of the electric device. The electric device receives the request, and registers the external device that issued the registration request as an event notification destination. When an event occurs in the electric device, the electric device obtains registered notification destinations, and transmits event information indicating the event to all the notification destinations. In this system, in a case that the number of events which occur in the electric device is abruptly increased or in a case that the number of external devices registered as event notification destinations is abruptly increased, there is a possibility of occurrence of event notification error since notification processing cannot catch up with occurred events. This problem becomes particularly notable upon event transmission by TCP (Transmission Control Protocol) instead of UDP (User Datagram Protocol) broadcasting. Accordingly, there is a need for a system to infallibly notify external devices registered as notification destinations of event information and control event processing load before the electric device reaches a processing limit. Further, in a case that an external device which is registered as an event notification destination is a notebook PC or the like, there is a possibility that the PC is removed from the network while the registration of the PC is not released. In this case, event notification is made to the PC upon occurrence of event, and since no response is returned from the PC, a time-out will occur in the TCP transmission. These wasteful processings increases the load on the electric device. Accordingly, a system to release event notification registration in accordance with some conditions is needed.
As a system to release event notification registration, a system to automatically release event notification registration after an elapse of a predetermined time period is known. However, the predetermined time period is fixed or designated from an external device. Accordingly, there is a possibility that the external device issues a registration request regardless of situation of the electric device, to bring the electric device into heavily-loaded status and cause an event information notification error.